The present invention relates to a method for manufacturing rubber mixtures in which in a first step in a ram mixer a base mixture is produced from rubber and non-reactive additives in a batchwise manner and in which in a second step the base mixture, without being stored intermediately, is finished in a ramless mixer in a batchwise manner by adding reactive additives at a reduced temperature.
In the known methods of the aforementioned kind the cooling within the ramless mixer is in general sufficient to cool the base mixture below the scorch time limit and furthermore to mix homogeneously the reactive additives within the working cycle time. The working cycle of the base mixer, on the one hand, and of the finishing mixture, on the other hand, are to be adjusted relative to one another.
With especially large mixing units and/or for very viscous or rapidly curing mixtures, for example, adhesive mixtures for metals, the difficulty may result that the cooling and finishing mixing in comparison to the mixing of the base mixture requires more time. Under these conditions an economical operation of a batch-type operation is no longer possible.
These disadvantages are to be eliminated with the present invention. Accordingly, the present invention has the object to provide a method that ensures an adaptation of the working cycle during base mixing and finishing-mixing even when the aforementioned special conditions are present.